This application is based on and incorporates herein by reference Japanese patent application No. 2000-130813 filed Apr. 28, 2000.
The present invention relates to a load drive circuit used for driving a load such as a motor or a solenoid.
In recent years, semiconductor switching devices are employed for accomplishing electric load control. However, the semiconductor switching device becomes large as the load becomes large, resulting in lessening yield, deterioration in packaging quality and high cost.
It is therefore proposed to drive a plurality of semiconductor switching devices in parallel for driving a load, so that power provided for each semiconductor switching device is lowered. Thus, the semiconductor switching devices can be sized small.
However, since the switching devices are driven with a large current, the resistances of wiring conductors of wiring conductor patterns which are connected to the semiconductor switching devices become more significant as the on-resistances of the semiconductor switching devices are decreased. Particularly in the case of driving the semiconductor switching devices in parallel, power concentrates on one of the semiconductor switching devices due to the difference between the resistances of the wiring conductors which constitute current paths through the respective semiconductor switching devices. Thus, the switching devices tend to overheat.
The present invention has an object to alleviate the influence of wiring conductor resistances of the wiring conductor patterns connected to semiconductor switching devices.
According to the present invention, a plurality of switching circuits are connected in parallel to drive an electric load jointly. One side of the parallel arrangement of the switching circuits is connected to a power source through a first wiring conductor pattern, and the other side of the parallel arrangement of the switching circuits is connected to the load through a second wiring conductor pattern. The first wiring conductor pattern and the second wiring conductor pattern have a first connecting portion connected to the power source and a second connecting portion connected to the load, respectively. Current paths from the first connecting portion to the second connecting portion through the switching circuits are formed to have the same resistance.
Most preferably, the first connecting portion and the second connecting portion are disposed in the vicinity of one end and the other end of a parallel arrangement of the switching circuits, respectively, so that the current paths have substantially the same path length.